Ninhydrin test – Its Principle, Reagents, Procedure etc

Ninhydrin test: ( Triketo Hydrindene Hydrate)

Both free and combined α-amino acids give Ninhydrin test.

Significances:

Ninhydrin test is used for the detection of amino acids in a solution. Ninhydrin When reacts with ammonia forms a dark blue or purple colour known as Ruhemann’s purple. So amino acid detection a solution mainly occurs  by performing ninhydrin test.

REAGENTS:

• Original solution (Protein Containing solution).
• Ninhydrin Reagent

PRINCIPLE:

Ninhydrin is the powerful oxidising agent. It causes oxidative decarboxylation of amino acids, i.e., Amino acids, on heating with ninhydrin, are oxidatively decarboxylated, producing carbon dioxide (CO2), ammonia (NH3), and an aldehyde. Reduced ninhydrin then reacts with the liberated ammonia and a blue or purple coloured complex is produced.

PROCEDURE:

• Take 1ml of original solution (protein solution) in a test tube.
• Add 2-3 drops of freshly prepared 0.5% ninhydrin solution.
• Heat to boil the test tube.

Also check: Millon’s test – Its Principle, Reagents, Procedure etc

INDICATION:

A blue or purple colour appears, if proteins, peptides or amino acids are present.

RESULT:

If you carefully follow all the steps mentioned above step by step then When blue or purple colour appear that mean Amino acid is present.

Precautions:

Before you perform ninhydrin test for amino acids, here is a list of precautions that you need to take care of before and while performing the experiment.

• Wash the apparatus before and after the experiment.
• Make sure that amount you are taking of samples and liquid drops are the same as mentioned in the procedure.
• Also, make sure that the test tube you are using must be clean and wash very neatly. There must not remain any impurity other than the natural stuff present in the test tube.
• Observe colours at the end of the tests very carefully and note down results on a notepad to avoid future inconvenience.
• Prevents prolonged heating of the test tube otherwise, it will give a false result.
• Carefully handle all the chemicals.